Association of COPD and Asthma COPD Overlap (ACO) with World Trade Center (WTC) occupational exposure intensity

Introduction: Reports and associations of COPD and ACO with WTC occupational exposures have been inconsistent. Using spirometric case definitions, we examined that association in the largest WTC occupational surveillance cohort. Methods: We tested for association between ACO and COPD and early arrival (within 48 hr, when dust and fumes exposures were more intense) at the 2001 WTC disaster site in workers with at least two spirometries between 2002 and 2018. Case definitions of COPD required fixed obstruction, and, for ACO pre-bronchodilator obstruction with >400 ml FEV1 response to bronchodilator. We used a nested 1:4 case-control design matching on sex and height (within 5 cm) using density sampling. We imputed missing data. Results: The study population consisted of 17,996 former WTC workers, predominantly (85.4%) male and overweight or obese (85.6%), of whom 586 (3.3%) and 258 (1.4%) cases met the COPD and ACO case definition, respectively. In adjusted analyses, COPD and ACO were associated with early arrival at the WTC site, with adjusted odds ratio, and 95% confidence interval of 1.3, 1.03-1.64, and 1.66, 1.1-2.49, respectively, independently from covariates such as smoking, age, cohort entry period, metabolic syndrome indicators, and high peripheral eosinophil count, among others. Discussion: In this cohort of WTC workers, spirometrically defined COPD and ACO were both associated with WTC exposure intensity. With substantially lower prevalence and effect sizes, we confirmed the findings from another cohort where the case definitions were based on self-reported physician diagnoses (PMID 32930623).